We camped, hiked, built team fires, climbed rocks and woke up with the sun for sunrise yoga. We immersed ourselves in healthspan practices including spending time in nature, resetting our circadian rhythms by rising early and eating before dark, and eating real food — mostly fish, raw fruits and vegetables, and whole grains. We practiced “leave no trace” and picked up trash where we saw it. And other than a singular satellite phone (we are a tech company, after all, and we needed to monitor for issues with our cloud platform for precision health!), we had no cell or internet service for three days — we unplugged and enjoyed the silence and fresh air of the campground around Fehr Lake.
Being scientists, we can’t help but appreciate the physiological and mental health benefits of temporarily leaving our desks, computers and cloud software and immersing ourselves in forest air.
We Are Wired To Be Outside
When we first see Elizabeth Bennett, in the 2005 film of Pride and Prejudice, she is walking through a field…
When Florence Williams starting using U.K. social scientist Dr. George Mackerron’s Mappiness mobile app, an iPhone app that collects information from people on-the-go about when, where and why they are happiest, she discovered something that intrigued her. She found that for herself and for other Mappiness users, when pinged at work people are generally unhappy, but when pinged while outside, people are extremely happy!
Being in nature can help us live in the present moment, or practice mindfulness, a key component of subjective well-being or happiness.
More than half of the world’s population now lives in urban areas, and that looks to increase to 70% by 2050. Living in cities and urban areas has many health benefits, such as access to modern medical centers. But urban dwelling can also deprive us of the affective and cognitive benefits of nature experience and increase our chronic stress levels. Did you know that the average American spends as much as 90% of his/her life inside of buildings? That’s 1,300 minutes of the 1,440 minutes in each day. Do you spend more than 2–3 hours outside on a daily basis? That makes us think we need to go out and buy more house plants this instant…
“[People] underestimate the degree to which even brief contact with the natural environment will benefit their well-being.” — Nisbet & Zelenski, via The effect of contact with natural environments on positive and negative affect: A meta-analysis
Bathing in Nature’s Spring of Youth
There is both correlational and experimental evidence for a range of health benefits associated with exposure to nature. It’s not just about escaping noise and pollutants — nature has intrinsic benefits to our health, both direct and indirect.
More directly, green spaces may improve air quality and increase the diversity of microbes and other antigens we are exposed to. This potentially leads to lower prevalence of early childhood asthma and allergies. It looks like biodiversity in our environment is strongly related to how our immune systems react to “foreign” bodies.
“Interactions with natural environmental features not only may increase general human well being in urban areas, but also may enrich the commensal microbiota and enhance its interaction with the immune system, with far-reaching consequences for public health.” — Hanski and colleagues, Environmental biodiversity, human microbiota, and allergy are interrelated
Spending time in natural environments is associated with reduced incidence of heart disease and all-cause mortality, or in other words, longer health and lifespan. There may be many explanations for the link between nature experiences and healthspan, including increased physical activity levels for people exposed to natural greenness. But it looks like access to green environments is important especially for low socioeconomic status groups.
“When people view vegetation…, the visual complexity may provide restoration from “directed attention”; that is, where specific focused attention is required for activities. […] Individuals can experience improved mental health through attention restoration in which a person’s mental fatigue is reduced and cognitive function restored.” — Shanahan and colleagues, Toward Improved Public Health Outcomes From Urban Nature
People seem to just feel better when they can see and experience nature. People living in areas with lots of green space perceive themselves as healthier than do residents of more urban areas. Views of natural, green environments have even been shown to reduce the length of hospital stays.
Perceptions also matter when it comes to nature experiences and our health. For example, in a study published in BioScience in 2012, participants who perceived greater species richness of birds, butterflies and plants in their surroundings also expressed greater feelings of well-being. But these feelings of well-being were independent of how much actual species diversity was present. People who believe that they live in a place with a high level of “greenness” are more likely to have better physical and mental health, suggesting that there are factors at play other than biodiversity itself. For example, people who perceive their spaces as “green” and beautiful may be more likely to walk, interact with others outside, etc.
Finally, exposure to nature can reduce stress, improve mental health and improve cognitive ability. A study of data from the 2008 Scottish Health Survey suggests that exercising in natural environments such as woods or forests is associated with a lower risk for mental health issues as compared to exercising in non-natural environments.
The Natural Stress Reducer
What’s more, stress reduction and mindfulness activities in nature may be more beneficial than these same activities performed inside buildings without a view or in other urban environments. For example, a 2010 experiment published in the Journal of Health Psychology found that the stress-relieving effects of gardening outperform the stress-relieving effects of other recreational activities such as reading.
“Stress-relieving effects of gardening were hypothesized and tested in a field experiment. Thirty allotment gardeners performed a stressful Stroop task and were then randomly assigned to 30 minutes of outdoor gardening or indoor reading on their own allotment plot. Salivary cortisol levels and self-reported mood were repeatedly measured. Gardening and reading each led to decreases in cortisol during the recovery period, but decreases were significantly stronger in the gardening group. Positive mood was fully restored after gardening, but further deteriorated during reading.” — Berg and colleagues, Gardening Promotes Neuroendocrine and Affective Restoration from Stress
One explanation for the benefits of spending time in nature on our health is the stress reduction theory. According to this theory, “exposure to environments with water, vegetation, expansive views, and other elements that contributed to the survival of our ancestors produces an unconscious autonomic response characterized by decreased physiological arousal, decreased negative affect, and increased positive affect. In other words, people are less stressed, physiologically and psychologically, when observing or present in […] natural environments,” accordign to McMahan & Estes, 2015.
In keeping with the stress reduction theory, nature contact following an acutely stressful event (an exam, a big deadline at work, etc.) can blunt associated negative thoughts and physiological responses. For example, our bodies respond to acute stress by raising blood pressure, stress hormone levels such as cortisol, heart rate, muscle tension and inflammation. Contact with nature can help mitigate these physiological stress responses and help us more quickly return to a “normal” state. For example, exposure to green spaces has resulted in improved regulation and cycling of the stress hormone cortisol. Cortisol has important functions in our body, but if it remains elevated for long periods of time, it can cause damaging levels of inflammation in the body and negatively impact the function of our immune system.
Another explanation for the restorative effect of spending time natural environments is the attention restoration theory. According to this theory, urban living and its associated noise (think of your computer and smartphone constantly pinging you) taxes your attention and leads to cognitive fatigue. This make sense when we consider research findings that time spent in nature helps improve working memory and mood. As restorative environment researcher Terry Hartig explains in a podcast summary of a recent Annual Review of Public Health article on Nature and Health, the natural environment provides fewer stressful exposures — less noise, less crowding, no deadlines, fewer bells and alarms — than people typically confront in their normal, smartphone-filled, urban lives.
A multitude of studies have revealed that nature experiences can reduce feelings of anger, fatigue, anxiety and sadness. But exposure to nature appears to do more than alleviate everyday life stressors and cognitive overload. The physical and mental health benefits of nature experiences are also linked to positive feelings, increased energy and emotional restoration.
“[A]ttention restoration theory proposes that the natural world is cognitively restorative and both facilitates recovery from mental fatigue and offers opportunities for reflection.” — Dallimer and colleagues, Biodiversity and the Feel-Good Factor
“When a person can engage with the natural environment, for example when they find it beautiful and interesting, when they can explore and take an interest in what birds and other animals are doing, when they can become fascinated by some plant or water moving in a stream — that may reinforce a psychological distance from stressful demands […] and promote restoration,” Dr. Terry Hartig explains in an Annual Review of Public Health podcast summary of Nature and Health.
Your Brain on Nature
In a study published in PNAS in 2015, researchers at Stanford University and the Laureate Institute for Brain Research found that a 90-minute walk through a natural environment (for example with views of trees, grass and rolling hills) can lower people’s reported levels of rumination, a repetitive thought process focused on negative aspects of the self. A 90-minute nature walk reduced blood flow and neural activity in the subgenual prefrontal cortex (sgPFC), an area of the brain associated with behavioral withdrawal, rumination and depression, while a walk through an urban environment (for example, along busy streets) didn’t have this beneficial effect. Similarly, studies have shown that “green exercise” or physical activity in the presence of nature can significantly improve self-esteem and mood.
“[D]ecreased nature experience may help to explain the link between urbanization and mental illness.” — Bratman and colleagues, 2015
In a small 20-person study published in Journal of Affective Disorders in 2012, people with major depressive disorder who walked for 50 minutes in nature, but not people who walked in an urban environment, performed better on memory span tests and showed improvements in mood. Follow up studies have strengthened our confidence that these results are not a fluke — nature experiences consistently improve working memory, lower anxiety and suppress rumination. People who visit natural spaces, from forests to coasts, feel restored.
“A growing body of empirical research suggests that brief contact with natural environments improves emotional well-being.” — McMahan & Estes, The effect of contact with natural environments on positive and negative affect: A meta-analysis
Don’t Worry, Be Happy — Nature Does it
Have friends and family members ever told you to stop worrying so much? Did it help? Probably not. Negative thought patterns like worry and rumination can be very difficult to “will away.” In fact, thinking about not thinking negative thoughts about ourselves or about the stresses in our lives can actually just give them more power (more about this in The Telomere Effect).
While we can’t will our stress, negative thoughts or sadness away, we can engage in activities known through scientific research to improve our happiness or sense of well-being. These include a variety of pleasant hobbies and activities informed by personal goals, physical activity, relaxation, meditation, problem solving, socializing, writing gratitude letters or otherwise practicing optimistic thinking, and spending time in nature.
“Escape from physical and social stressors has long been described as an important motive for recreation in natural areas.” — McMahan & Estes, The effect of contact with natural environments on positive and negative affect: A meta-analysis
It’s Physiological, Too
The positive impacts of spending time in nature transfer not only to our levels of happiness and cognitive function, but also to how our bodies function and even how long we live.
Terry Hartig and colleagues have found that walks in nature, or even sitting by a window with tree views, can reduce blood pressure more quickly after a stressful task than walking in an urban surrounding or sitting by a window without a “green” view. Walks in nature also improve attention test performance and decrease self-reported levels of anger.
“Walking in the forest environment may promote cardiovascular relaxation by facilitating the parasympathetic nervous system and by suppressing the sympathetic nervous system. In addition, forest therapy may be effective for reducing negative psychological symptoms.” — Lee and colleagues, Influence of Forest Therapy on Cardiovascular Relaxation in Young Adults
Psychological stress reduction and faster recovery from stressful events, both benefits of nature experiences, have other downstream physiological benefits. Stress, especially chronic stress, raises levels of stress hormones, oxidative stress and inflammation in our bodies and brains. Interventions that reduce somatic stress and inflammation, including antioxidant intake (fruits and vegetables!), intermittent fasting, physical activity and yes, even meditation and time spent in nature, can protect our bodies from the damaging impacts of long-term stress, from immune suppression to deregulation of metabolic processes.
Nature experiences may also have impacts on our health mediated by environmental exposures, for example through reduced exposure to air pollutants. Even indoor plants can significantly improve the air quality of our homes. Indoor plants including English ivy and spider plants have been shown to reduce levels of many volatile organic compounds.
Access and time spent in natural environments may also increase our daily physical activity levels and promote social cohesion. There are both mental and physical health benefits to enjoying nature with others, such as enjoying a morning run with friends, a trail walk with your kids or a picnic with your significant other.
A 2008 research report in the Journal of Epidemiology & Community Health found that increases in physical activity and social interaction within natural spaces may help explain the connection between time spent in these spaces and improvements in mental and physical health. People with stronger social relationships and people who get recommended levels of daily physical activity tend to live longer and live healthier. The good news for nature lovers is that nature experiences, urban green spaces and green neighborhoods may foster both physical activity and social cohesion.
How much nature is enough nature?
When it comes to exposure to nature, more is better. But especially for urban dwellers, every bit of nature experience counts. There are even some correlational studies showing that “green” window views are associated with better memory, attention, impulse control among children, and sense of well-being among adults.
“For girls, green space immediately outside the home can help them lead more effective, self-disciplined lives.” — Taylor and colleagues, 2002
People who visit outdoor green spaces for durations of at least 30 minutes or more over the course of a week may reduce their levels of depression and blood pressure by approximately 10%, according to a study on the health benefits of nature experiences by dose in Nature Scientific Reports. What constitutes “enough” green exposure in urban environments? One study suggests that we need access to spaces with more than 20–30% vegetation cover to experience mental health benefits (lowered depression, anxiety and stress). But exposure to undisturbed, wild nature areas is ideal.
“Incorporating brief ventures in nature into one’s daily routine may thus be one relatively easy and enjoyable way to achieve sustainable increases in SWB” — McMahan & Estes, “The effect of contact with natural environments on positive and negative affect: A meta-analysis”
Clean air, clean water, safety, daily physical activity, access to healthy food and exposure to nature are basic components of a healthy environment for humans. If you live in a city, it may be worth visiting a local park or driving out to a wooded area once or twice in a week, in order to soak in healthspan-boosting clean air, natural sounds and green views.
“Chronic pain levels increase with age, and capabilities and challenges faced decline. These are offset, however, by greater attention and appreciation of natural surroundings. Of particular significance, enjoyment and opportunities for euphoria persist despite ageing, and euphoria can temporarily override chronic pain, stress and fatigue. […] By providing opportunities for euphoria as well as exercise, adventurous outdoor nature sports can make substantial contributions to the physical, mental and social health of older individuals.” — Buckley, Nature sports, health and ageing: the value of euphoria